(function() {
    var root = this
    var SymbolPolyfill = function Symbol(description) {
        if(this instanceof SymbolPolyfill ) {
            throw new TypeError('Symbol不能被new')
        }
        var descString = description === undefined ? description:String(description)
        var symbol = Object.create(null)
        Object.defineProperties(symbol,{
            '__Description__':{
                value:descString,
                Writable:false,
                enumerable:false,
                configurable:false
            }
        })
    } 
})()
let a = SymbolPolyfill('123')
console.log(a);